• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.5
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• pp.487-493
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• 1999

To predict the background level of harmonics produced by household appliances, information on the site, capacity, and usage pattern of these loads arenecessary. However, as household appliances are distributed widely and various in type, it is difficult to know these kinds of information accurately. This paper presents a method for estimation of background level of harmonics produced by distributed harmonic sources with readily available data. Large industrial customers are excluded from this study. In this paper, customers are grouped into three classes, i.e. residential, commercial, and industrial. Typical customers for each class are assumed and characteristics of their equipments are modeled. As the proposed method does not require harmonic measurement, it can be employed to forecast voltage total harmonic distribution (VTHD) in the future. An illustrative example is described.

• Speech Sciences
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• v.11 no.1
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• pp.7-20
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• 2004

In this paper, we propose a two-step noise compensation algorithm in feature extraction for achieving robust speech recognition. The proposed method frees us from requiring a priori information on noisy environments and is simple to implement. First, in frequency domain, the Harmonics-based Spectral Subtraction (HSS) is applied so that it reduces the additive background noise and makes the shape of harmonics in speech spectrum more pronounced. We then apply a judiciously weighted variance Feature Vector Normalization (FVN) to compensate for both the channel distortion and additive noise. The weighted variance FVN compensates for the variance mismatch in both the speech and the non-speech regions respectively. Representative performance evaluation using Aurora 2 database shows that the proposed method yields 27.18% relative improvement in accuracy under a multi-noise training task and 57.94% relative improvement under a clean training task.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.537-543
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• 2003

Transient vibration generated by developing localized fault in gear can be used as indicators in gear fault detection. This vibration signal suffers from the background noise such as gear meshing frequency and its harmonics and broadband noise. Thus in order to extract the information about the only gear fault from the raw vibration signal measured on the gearbox this signal is processed to reduce the background noise with many kinds of signal-processing tools. However, these signal-processing tools are often very complex and time waste. Thus. in this paper. we propose a novel approach detecting the damage of gearbox and analyzing its pattern using the raw vibration signal. In order to do this, the residual signal. which consists of the sideband components of the gear meshing frequent) and its harmonics frequencies, is extracted from the raw signal by the power spectral density (PSD) to obtain the information about the fault and is used as the input data of the artificial neural network (ANN) for analysis of the pattern of gear fault. This novel approach has been very successfully applied to the damage analysis of a laboratory gearbox.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.237-245
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• 2008

Recently, multilevel H-bridge inverters have become popular in medium to high power ac drive applications. One of significant advantages of them is low harmonic contents in their input line currents thanks to the transformer with multiple phase-shifted secondary windings. This paper attempts to provide basic guidelines for the design of the phase shifting transformer windings and theoretical analysis of input line current harmonics of H-bridge inverters. The part II is devoted to the analysis of the harmonic characteristics of the input line current, providing mathematical background for the equidistant phase-shifting angle distribution policy for harmonic elimination.

• Journal of Korea Multimedia Society
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• v.16 no.10
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• pp.1171-1179
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• 2013

Interactive audio service provide with audio generating and editing functionality according to user's preference. A spatial audio object coding (SAOC) scheme is audio coding technology that can support the interactive audio service with relatively low bit-rate. However, when the SAOC scheme remove the specific one object such as vocal object signal for Karaoke mode, the scheme support poor quality because the removed vocal object remain in the SAOC-decoded background music. Thus, we propose a new SAOC vocal harmonic extranction and elimination technique to improve the background music quality in the Karaoke service. Namely, utilizing the harmonic information of the vocal object, we removed the harmonics of the vocal object remaining in the background music. As harmonic parameters, we utilize the pitch, MVF(maximum voiced frequency), and harmonic amplitude. To evaluate the performance of the proposed scheme, we perform the objective and subjective evaluation. As our experimental results, we can confirm that the background music quality is improved by the proposed scheme comparing with the SAOC scheme.

• Phonetics and Speech Sciences
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• v.2 no.1
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• pp.77-85
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• 2010

This paper proposes an efficient feature vector processing technique to guard the Speech Emotion Recognition (SER) system against a variety of noises. In the proposed approach, emotional feature vectors are extracted from speech processed by comb filtering. Then, these extracts are used in a robust model construction based on feature vector classification. We modify conventional comb filtering by using speech presence probability to minimize drawbacks due to incorrect pitch estimation under background noise conditions. The modified comb filtering can correctly enhance the harmonics, which is an important factor used in SER. Feature vector classification technique categorizes feature vectors into either discriminative vectors or non-discriminative vectors based on a log-likelihood criterion. This method can successfully select the discriminative vectors while preserving correct emotional characteristics. Thus, robust emotion models can be constructed by only using such discriminative vectors. On SER experiment using an emotional speech corpus contaminated by various noises, our approach exhibited superior performance to the baseline system.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.1
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• pp.101-107
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• 2011

The background noises and distortions by channel are major factors that disturb the practical use of speech recognition. Usually, noise reduce the performance of speech recognition system DSR(Distributed Speech Recognition) based speech recognition also bas difficulty of improving performance for this reason. Therefore, to improve DSR-based speech recognition under noisy environment, this paper proposes a method which detects accurate speech region to extract accurate features. The proposed method distinguish speech and noise by using entropy and detection of spectral energy of speech. The speech detection by the spectral energy of speech shows good performance under relatively high SNR(SNR 15dB). But when the noise environment varies, the threshold between speech and noise also varies, and speech detection performance reduces under low SNR(SNR 0dB) environment. The proposed method uses the spectral entropy and harmonics of speech for better speech detection. Also, the performance of AFE is increased by precise speech detections. According to the result of experiment, the proposed method shows better recognition performance under noise environment.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.936-946
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• 2007

Analytical geopotential field in balance with the sectoral mode (the first symmetric mode with respect to the equator) of the Rossby-Haurwitz wave on the inclined rotation axis was derived in presence of superrotation background flow. The balanced field was obtained by inverting the divergence equation with the time derivative being zero. The inversion consists of two steps, i.e., the evaluation of nonlinear forcing terms and the finding of analytical solutions based on the Poisson's equation. In the second step, the forcing terms in the from of Legendre function were readily inverted due to the fact that Legendre function is the eigenfunction of the spherical Laplacian operator, while other terms were solved either by introducing a trial function or by integrating the Legendre equation. The balanced field was found to be expressed with six zonal wavenumber components, and shown to be of asymmetric structure about the equator. In association with asymmetricity, the advantageous point of the balanced field as a validation method for the numerical model was addressed. In special cases where the strength of the background flow is a half of or exactly the same as the rotation rate of the Earth it was revealed that one of the zonal wavenumber components vanishes. The analytical balanced field was compared with the geopotential field which was obtained using a spherical harmonics spectral model. It was found that the normalized difference lied in the order of machine rounding, indicating the reliability of the analytical results. The stability of the sectoral mode of Rossby-Haurwitz wave and the associated balanced field was discussed, comparing with the flrst antisymmetric mode.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.16 no.1
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• pp.23-27
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• 2005

Background and Objectives : Voice disorders can cause problems in patients with benign vocal cord lesions emotionally, physically, economically and functionally. Neither subjective nor objective voice examinations can evaluate such factors adequately. The Voice Handicap Index (VHI) subjectively evaluates voice disorders in terms of physical, functional, emotional factors and measures the patient's perception of the impact of voice disorder. The purpose of this study is to evaluate the usefulness of VHI in the patients with benign vocal cord lesions. Materials and Method : The authors evaluated 37 patients who experienced laryngeal microsurgery for benign vocal cord lesions from september 2003 to August 2004. The VHI was used to measure the postoperative changes of the patient's perception and acoustic analysis and aerodynamic tests were also done. Statistical analysis was done using paired t-test and Pearson's correlation. Results : The VHI scores showed statistically significant reductions postoperatively. In acoustic analysis, jitter and shimmer had statistically significant reductions after surgery but noise-to-harmonics ratio did not. A statistically significant change in the average MFR and MPT perioperatively was found. The relationship between VHI and acoustic, aerodynamic analysis attained statistical significance. Conclusion : The VHI is a useful assessment tool to monitor the patient's self-perception of voice change after the surgery of benign vocal cord lesions. The VHI measurement, when combined with acoustic and aerodynamic analyses, will be helpful in comparing functional outcomes after voice surgery.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.22 no.1
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• pp.40-46
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• 2011

Background and Objectives : Vocal fold bowing is an organic voice disorder that is associated with an abnormal structure of the vocal folds whereas vocal fold polyp is a functional voice disorder caused by an abnormal use of the vocal folds. Both types of vocal folds share a common property in that they make one's voice breathy or strained. The purpose of this study is to compare voice from two types of vocal folds and to offer information of clinical importance. Materials and Method: Vocal fold bowing and vocal fold polyp groups consisted of 7 male subjects, respectively. All subjects recorded /a/ in the state of measuring MPT (maximum phonation time), repeating 3 times, by a voice recorder (48 kHz sampling rate; 24 bit quantization). They answered the questions of K-VHI. Time domain parameters (such as perturbation parameters including HNR, Jitter, etc.) were calculated for the whole duration of /a/ and those of the frequency domain were measured in initial 40 ms and stable 40 ms of /a/, respectively. Mann-Whitney V-test was used for the time domain parameters and K-VHI survey, and Wilcoxon signed rank test was applied to the frequency domain parameters (H1, H2, H1-H2). Results: For K-VHI survey and the time domain analysis, there was no significant difference between bowing and polyp group. For frequency domain analysis, H1 and H2 showed a significantly different result between two groups. Vocal fold bowing group has longer duration and lower intensity than that of vocal fold polyp group in the 'aspirated interval', which could be observable prior to ordinary vowel oscillation. Conclusion: Both groups seem to show breathy voice. This could be referred on the basis of the value of H1-H2. The K-VHI survey says that subjects with vocal fold bowing feel more uncomfortable than subjects with vocal fold polyp.